PMC

Scale of lengths involved in coculture interactions can be very important in designing strategies for MSC differentiation. Modes of interaction between cell populations influence the growth and differentiation of MSCs by determining the local microenvironment. Cells from a mesenchymal lineage respond to influences exerted by morphological conditions as well as a range of factors that can be intracellular, matrix bound, or soluble. The availability and abundance of these factors is highly dependent on the spatiotemporal relation of the intercellular communication, thus making the study of these scales of length important to tissue engineering applications. MSC, mesenchymal stem cell.

(A) Micromass coculture: high volumes of cells may be pelleted together in a microcentrifuge tube. This micromass coculture allows for the study of signaling pathways without any interference from biomaterials present in a scaffold. Pelleted cells may then be placed into a well for further culturing or may be kept in the microcentrifuge tube. (B) Indirect coculture: cell populations may be cocultured without physical contact through use of a transwell system. This indirect coculturing allows for any soluble factors to be shared through media, while individual populations may be cultured using different techniques. For example, in this figure, chondrocytes are cultured in alginate beads above the monolayer culture of MSCs. (C) Ex-vivo coculture: explanted tissues maybe cocultured with cells as an ex-vivo study. This allows for the maintenance of the microenvironment of the explant while sharing any signaling molecules through the media. For example, culturing native tissue explants with target MSCs enable the solubilization of such factors that can otherwise be hard to synthesize in vitro or introduce exogenously. (D) Conditioned media: conditioned media studies may be used to evaluate the impact of cell secreted factors on differentiating cells. Conditioned media studies are often used to evaluate cell cross talk within cell signaling pathways.